The use of rapid cook ovens is intended to bring food portions to a serving temperature as quickly as possible, which generally means within 30-180 seconds of the order being placed. A second intention is the best possible quality of food portions. The very different behaviour of food when being heated makes achieving the goals challenging. The goals are best achieved using hybrid ovens using more than one heating technique. Most generally, the heat sources used nowadays in rapid cook ovens are microwave radiation devices and electrical resistances, which are arranged to heat air being circulated through the oven space.
Hybrid ovens utilizing hot air and microwaves as heat sources are known from, for instance, the publications WO 95/09519 and WO 99/52328. Publication EP 1930660 A1, which discloses a circulating-air oven equipped with microwave heating, is also known from the prior art.
Contamination is a problem in closed air-circulation ovens. Magnetrons in particular are sensitive to dirtying. Publication WO 98/54517 discloses an oven, in which there is closed air circulation and a catalyser for cleaning the air.
Oil cookers are used particularly for the heating of potato chips. Such a solution is disclosed in, for instance, publication WO 98/54517. Known hybrid ovens do not have oil cookers. The main problem with oil cookers is dirtying of the oil. Publication WO 2008/144290 discloses an oil filtering technique. Further, the use of a cooker to heat frozen products creates a great deal of steam. A problem with ovens of the prior art is that several different devices are required to make a food portion, in which the components of the food portion are prepared at different temperatures and simultaneous preparation is difficult.